How Lifecontinues

Chapter 11

Chapter 10

Heredity

“...tendency for traits to be passed from parent to offspring.”

Traits

“...alternative forms of a character, or heritable feature.”

×

×

×

×

×

×

×

×

Dominant Form RatioF2 Generation

Dominant: RecessiveRecessive Form

Purple flowers White fowers

Yellow seeds Green seeds

Round seeds Wrinkled seeds

Green pods Yellow pods

Axial flowers Terminal flowers

Tall plants Dwarf plants 2.84:1(3/4:1/4)

3.14:1(3/4:1/4)

2.95:1(3/4:1/4)

2.82:1(3/4:1/4)

2.96:1(3/4:1/4)

3.01:1(3/4:1/4)

3.15:1(3/4:1/4)

705:224

6,022:2,001

5,474:1,850

428:152

882:299

651:207

Inflated pods

787:277

TABLE 10.1

Character

SEVEN CHARACTERS MENDEL STUDIED IN HIS EXPERIMENTS

Constricted pods

Can we figure out if a purple-flowering plantis Pp or PP?

Testcross

Mendel’s Theory of Heredity

Parents do not transmit traits directly; they transmit trait information in the form of “factors”

Each parent has two copies of a trait factor

Alternative forms of a factor (alleles) lead to alternative traits

The two alleles an individual has do not affect each other

The presence of an allele does not guarantee that a trait will be expressed

Homozygoushave two alleles that are the same

Heterozygoushave two alleles that are different

For a certain trait, an individual can be...

Mendel’sLaw of Segregation

Two alleles of a trait separate during the formation of gametes; half the gametes carry one and half carry the other

Mendel’s Law of IndependentAssortment

Inheritance of one trait does not influence the inheritance of another trait

Many traits exhibit Mendelian inheritance

Genes

The Central Dogma

Phenotype

Genotype

Mendel’s Theory of Heredity

Parents do not transmit traits directly; they transmit trait information in the form of genes

Each parent has two copies of a trait gene

Alleles, alternative forms of a gene, lead to alternative traits

The two alleles an individual has do not affect each other

The presence of an allele does not guarantee that a trait will be expressed

Chromosomes

Section 8.3

Section 9.3

Fig. 10.6

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

p

Locus for firstgene containingallele P or p

Locus for secondgene containingallele Y or y

Paternal homologue

Homologouschromosomes

Maternal homologueY

Homozygousgenotype YY

YP

Heterozygousgenotype Pp

Two kinds:

Autosomes

Sex Chromosomes

Sickle-CellDisease

Autosomal Recessive

Huntington’s Disease

Autosomal Dominant

Mitosis

The division of cells

Co 8

Section 8.4

Section 9.4

Meiosis

The formation of gametes

Sections 9.1 - 9.4

Sections 8.1 - 8.4

Page 183

Many traits do not follow Mendelian Inheritance

Sex-Linked Traits

http://www.uic.edu/classes/bms/bms655/lesson6.html

X-Linked Dominant

X-Linked Dominant[A] mode of genetic inheritance by which a dominant gene is carried on the X chromosome. As an inheritance pattern, it is less common than the X-linked recessive type. In medicine, X-linked dominant inheritance indicates that a gene responsible for a genetic disorder is located on the X chromosome, and only one copy of the allele is sufficient to cause the disorder when inherited from a parent who has the disorder.

http://en.wikipedia.org/wiki/X-linked_dominant

http://www.uic.edu/classes/bms/bms655/lesson7.html

X-Linked Recessive

X-Linked Recessive

http://en.wikipedia.org/wiki/X-linked_recessive

[A] mode of inheritance in which a mutation in a gene on the X chromosome causes the phenotype to be expressed (1) in males… and (2) in females who are homozygous for the gene mutation...

X-linked inheritance means that the gene causing the trait or the disorder is located on the X chromosome.

X-Linked Recessive

Red-Green Color BlindnessHemophilia AHemophilia BDuchene Muscular DystrophyBecker’s Muscular Dystrophy

http://en.wikipedia.org/wiki/X-linked_recessive_inheritance

Polygenic Inheritance

“When multiple genes act together to influence a character such as height or weight...”

Continuous Variation

Pleiotropic

“Often, an individual allele has more than one effect on the phenotype.”

Sickle-Cell Disease

Cystic Fibrosis

Incomplete Dominance

“...a heterozygous phenotype that is intermediate between those of the parents.”

Epistasis

“...an interaction between the products of two genes in which one of the genes modifies the phenotypic expression produced by the other.”

Codominance

“...the effects of both alleles are expressed.”

Environmental Effects

Linkage

Homologous Recombination

Mendel’s Law of IndependentAssortment

ChromosomalDisorders

Somatic cells are diploid

Gametes are monoploid

Nondisjunction

“The failure of chromosomes to separate correctly during meiosis I or II...”

108

Figure 10.24 Nondisjunction in anaphase ICopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Metaphase l

Anaphase l

Nondisjunction:homologouschromosomes failto separate

Metaphase ll

Results in four gametes: two are n+1 and two are n–1

Aneuploidy

“...an abnormal number of chromosomes.”

Down Syndrome

trisomy 21

Nondisjunctionof sex chromosomes

113

X

Y

O

XX

Nondisjunction

XX

Eggs

XOXXX

Female(Turner

syndrome)

Female(triple X)

OY

NonviableMale

(Klinefeltersyndrome)

XXY

SpermXY

Male

Female